I tried to change the CPU board on a MDD from a single 1.25 to a dual 1.25. I changed the heat sink to the copper one for the dual 1.42. At first I was still having heat issues, which I could not understand since I was using the heat sink from a faster model, but either way I replaced the 120mm fan and added two 60mm to the case behind the heatsink. Now my temps look fine in temp monitor, but It is freezing up at seemingly random times. Sometimes I can use it all day with no problem, and then sometimes I can only use it for 10 to 30min before it freezes. At first I did not think that it could be the CPU board. I just completed a full, from scratch reload of OS X tiger, and it was still doing it, so I put back in the single 1.25 and so far no issues. I have been running the 1.25 for about an hour so far Anyone have any ideas? I am running out of ideas.

Did you use a thermal compound on the cpus? If not shut it down and get some. I use articsilver 5. The mdd duals do run hot, but should not shut down if the area isnt too warm.After that, you may want to make sure that the firmware is up to date.-maestro

have you checked if NAP mode is still on? use CHUD tools to do so. NAP mode has been used to cool down the cpu by shutting it down when idle. sort of.

i heard that single MDDs have nap enabled by default, while duals tend to crash randomly in exactly the way you described. i would suspect firmware decides wether nap is on or off by default. do not ask me how to have nap mode disabled by default at every startup on an original single CPU-machine.

i used a dual MDD for over 1 year and experienced these freezes when nap was enabled. (thats why i had to cool it down by other means and made that unreal mod)

anyway; if you have NAP mode disabled already, i also have no clue.regardsgodicm

I have checked to make sure that nap mode is turned off, and it is. I am completely lost right now, and am only left to think that maybe the CPU board is bad. I am going to try to get another. Thank you to everyone who tried to help.

The Dual 1.25 167 bus CPUs are getting hard to come by and the 1.42 CPUs are all but impossible. Oh well, maybe someone will get an upgrade out soon or I am just going to have to take the plunge into a G5.

Does anyone know if the CPU board has a firmware or just the logic board. I am trying to figure out all the possible reasons that would cause my problems, and I think that we have already gone though them all here.

Xplain's use of MacNews, AppleCentral and AppleExpo are not affiliated with Apple, Inc. MacTech is a registered trademark of Xplain Corporation. AppleCentral, MacNews, Xplain, "The journal of Apple technology", Apple Expo, Explain It, MacDev, MacDev-1, THINK Reference, NetProfessional, MacTech Central, MacTech Domains, MacForge, and the MacTutorMan are trademarks or service marks of Xplain Corp. Sprocket is a registered trademark of eSprocket Corp. Other trademarks and copyrights appearing in this printing or software remain the property of their respective holders.

All contents are Copyright 1984-2010 by Xplain Corporation. All rights reserved. Theme designed by Icreon.